Sulfurized olefins, e.g. sulfurized isobutylene and lubricant compositions containing such sulfurized isobutylene, are well known in the art as lubricant additives imparting extreme pressure and antiwear capabilities.
The metal surfaces of machinery or engines operating under heavy loads, wherein metal slides against metal, may undergo excessive wear or corrosion. Often the lubricants used to protect the metal surfaces deteriorate under such heavy loads and as a result, do not prevent wear at the points of metal to metal contact. Consequently, the performance of the machine or engine will suffer, and in aggravated cases the machine or engine may become completely inoperative. While sulfurized olefins have shown some benefit when added as lubricant additive, in many instances their application is limited since some types of sulfurized olefins have: an undesirable corrosion property (especially towards copper), generate malodorous by-products in operation, and/or have stability and compatibility issues.
Sulfurized olefins have been extensively used in many lubricant applications requiring extreme pressure/antiwear activity. These sulfurized olefins which include sulfurized C3-C8 olefins such as isobutylene are described by U.S. Pat. Nos. 3,703,504; 3,703,505; and 3,873,454. These patents and U.S. Pat. No. 4,240,958 generally employ methods of preparing their sulfurized products wherein the olefin is sulfohalogenated with a sulfur halide at some stage in their synthesis.
Sulfurized olefins have also been prepared by the direct sulfurization of olefins with sulfur and hydrogen sulfide, see U.S. Pat. Nos. 2,337,473; 4,119,549; 4,119,550; 4,191,659; 4,344,854 and 4,147,640. U.S. Pat. No. 4,147,640, for example, describes the sulfurization of various olefinic hydrocarbons such as dicyclopentadiene with sulfur and hydrogen sulfide. Also disclosed are methods of preparing sulfurized compounds by contacting an olefinic feedstock with sulfur and hydrogen. The olefin can be isobutene and the catalyst can be ammonia or an amine, typically these products are alkyl-alkenyl polysulfide mixtures and polymeric polysulfides.
The direct sulfurization of olefins such as diisobutylene and triisobutylene with sulfur is described, for example, in U.S. Pat. Nos. 2,995,569 and 3,796,661. When triisobutylene is employed, these patents describe the formation of exclusively 4-neopentyl-5-tertiary butyl-1,2-dithiole-4-cyclopentene-3-thione with a minor amount of organic sulfides and polysulfides. The direct sulfurization process employed elevated temperatures at both low and elevated pressures. U.S. Pat. No. 3,697,221 discloses of several 1,2-dithiole-3-thione derivatives as intermediates to the thionium methosulfates. U.S. Pat. No. 4,042,514 discloses of alkylthio and alkylarylthio derivatives of 1,2-dithiole-3-thiones. U.S. Pat. No. 4,194,980 discloses cyclic sulfurized olefins prepared by reacting an olefin with a cyclic polydisulfide. U.S. Pat. Nos. 3,345,380, 2,535,706, 2,535,705 describe methods of making various thiones by reacting elemental sulfur and isobutylene and other unsaturated hydrocarbons. U.S. Pat. No. 3,364,232 discloses high molecular weight trithiones prepared by reacting an olefin of at least 30 carbons in the presence of sulfur and a substituted trithione.
Thus, it is well known that many methods have been used for producing organic sulfides by treating olefins. It is also well known that many sulfurized organic compositions are useful as lubricant additives. Some of the prior art teaches that thiones are undesirable especially high levels of thiones, such as dithiol-thiones (or dithiolethiones), or high levels of thiones in combination with various complex sulfurized mixtures. Typically these thiones need to be removed. Dithiolethione-free sulfurized olefin compositions have been prepared by the reaction of sulfur, isobutylene and hydrogen sulfide as exemplified by U.S. Pat. No. 4,344,854 noted above, or U.S. Pat. No. 5,135,670 also employing a sodium sulfate nonahydrate, and for example U.S. Pat. No. 5,338,468 employing elemental sulfur, isobutylene and an amine base. U.S. Pat. No. 5,849,677 discloses extraction of 4-methyl-3H-1,2-dithiole-3-thione (“MDTT”) from a sulfurized olefin feed stream using solvent extraction.
It has now been discovered that the reaction of sulfur and a highly reactive methylvinylidene polyisobutylene produces a low odor, sulfurized polyisobutylene reaction product having anti-wear, extreme pressure load capacity, and antioxidant characteristics; which is suitable for use, for example, as a lubricant additive. Such reaction product and resulting polyisobutyl-1,2-dithiole-4-cyclopentene-3-thiones reaction products are thermally more stable relative to the conventional sulfurized isobutylene, do not have a strong odor, and are anticipated to be more stable in the presence of acids. Accordingly, there is a need for methods to prepare and use these reaction products, to the components themselves as well as mixtures thereof, and to compositions employing them.